Field of the Disclosure
The present disclosure relates to a voice coil motor.
Description of the Related Art
Recently, a small optical device such as a super-small digital camera on a mobile phone or a high resolution digital camera has been developed and is formed with an actuator for adjusting magnification and focus. The camera on the mobile phone or the digital camera recently employs an actuator such as a VCM (voice coil motor) on a wide range base.
The conventional super-small digital camera on the mobile phone is such that it is impossible to adjust a gap between an image sensor and lens, and a lens driving device such as a VCM for adjusting the gap between the image sensor and the lens has been developed to allow the super-small digital camera to capture an improved image.
The VCM is a motor that uses a force from a magnetic field generated by a magnet and a magnetic field generated by a coil block facing the magnet, such that the VCM is adequate in adjusting a gap between a lens and an image sensor in a camera module to enable obtainment of an improved image from the mobile phone.
A conventional VCM employed for the super-small digital camera used to be unable to adjust a gap between a lens condensing outside light and an image sensor converting the outside light to an image.
The conventional VCM includes a cylindrical bobbin mounted therein with a lens, a coil block wound with a coil at a periphery of the bobbin, and an elastic member elastically supporting a magnet opposite to the coil block and the bobbin.
The elastic member is coupled to a boss protruded from a bottom distal end of the bobbin, where the bobbin is moved upwards by a force generated by a magnetic field generated by the coil, and the elastic member elastically supports the bobbin.
However, the conventional VCM suffers from disadvantages in that a gap is frequently generated between the bobbin and the elastic member arranged under the bobbin by a manufacturing tolerance of the bobbin and the elastic member, and it is difficult to accurately adjust an interval between a lens and an image sensor due to the gap between the bobbin and the elastic member arranged under the bobbin.
Meantime, a part of a leaf spring is coupled to the bobbin by way of insert method, and to be more specific, the part of the leaf spring is injected along with the bobbin to couple the bobbin to the leaf spring when the bobbin is injected.
Alternatively, a boss formed at a distal end of the bobbin is coupled to the leaf spring, and the leaf spring coupled to the boss is coupled to the distal end of the bobbin by way of thermal fusion method.
In a case the part of the leaf spring is coupled to the bobbin by way of insert method according to the prior art, a manufacturing process becomes complicated to increase a manufacturing cost, and in a case the leaf spring is inserted into the bobbin to deform the leaf spring, the leaf spring and the bobbin are disadvantageously disposed of altogether.
Another disadvantage is that in a case the leaf spring is coupled to the bobbin by the thermal fusion method, the leaf spring is disengaged from the bobbin due to vibration and/or shock applied from outside, because an attachment strength between the bobbin and the leaf spring is smaller than that of the insert method.
Alternatively, an adhesive is coated between a distal end of the bobbin and the leaf spring to increase a coupling strength between the bobbin and the leaf spring. However, another disadvantage is generated that it is difficult to improve a coupling strength between the bobbin and the leaf spring due to smaller adhesive coated area between the leaf spring and the bobbin.
Still another disadvantage is that the coil electrically connected to the leaf spring is short-circuited due to the leaf spring being disengaged from the bobbin.
Still further disadvantage is that the bobbin and the leaf spring are mutually bonded by an adhesive, and in a case the bobbin and the leaf spring are bonded by the adhesive provided by a dispenser, the leaf spring is separated along with the dispenser when the leaf spring is separated after the adhesive is coated to the leaf spring using the dispenser, to damage the leaf spring and/or cause an adhesive imperfection to the bobbin and the leaf spring.